1. Field of the Invention
The invention relates to a brake control apparatus.
2. Description of the Related Art
There is known a brake control apparatus that electronically controls, by means of an actuator, the supply of brake fluid to wheel cylinders via a fluid pressure circuit to thereby adjust the fluid pressures supplied to the respective wheel cylinders (e.g., see Japanese Patent Application Publication No. 2007-437258 (JP-A-2007-437258)).
The brake control apparatus described in Japanese Patent Application Publication No. 2007-137258 (JP-A-2007-137258) is equipped with a main conduit that couples respective wheel cylinders to a master cylinder including a master reservoir storing brake fluid therein, pumps that suck in/discharge the brake fluid stored in the master reservoir to pressurize the respective wheel cylinders, pressure regulation conduits that are provided in parallel with the pumps respectively, and normally open linear valves that are disposed in the pressure regulation conduits respectively. Further, the brake control apparatus is equipped with a subsidiary conduit that couples the master cylinder to one or some of the wheel cylinders, and a control valve that is provided in the subsidiary conduit, for the sake of a failsafe in the event of an abnormality in brake control via the main conduit. In addition, the brake control apparatus is equipped with normally closed valves downstream of the linear valves respectively to prevent the brake fluid supplied to the wheel cylinders from flowing toward the main conduit side in supplying fluid pressures to the wheel cylinders respectively via the subsidiary conduit.
In the configuration of Japanese Patent Application Publication No. 2007-137258 (JP-A-2007-137258), during normal brake control, the pumps supply the brake fluid from the master reservoir to the respective wheel cylinders, thereby supplying fluid pressures to the wheel cylinders respectively and applying braking forces to wheels respectively. Further, the normally closed valves are energized to be opened, and the opening degrees of the linear valves are adjusted through energization control to adjust and hold the fluid pressures supplied to the wheel cylinders respectively. Thus, in the configuration of Japanese Patent Application Publication No. 2007-137258 (JP-A-2007-137258), the linear valves and the normally closed valves must be held energized to hold the fluid pressures supplied to the wheel cylinders respectively.
On the other hand, the linear valves and the normally closed valves are loaded through energization. Accordingly, in order to lengthen the period in which the respective valves operate normally and hence enhance the operating reliability of the brake control apparatus, it is desirable to minimize the period of energization of the linear valves and the normally closed valves.